On proper ice the ABS or no ABS argument is irrelevant - your tyres don't have any grip - period - the best way to tell if you are on 'proper' or black ice is that all your tyre noise will disappear. On gravel and loose snow the ABS can prevent the 'snow-plough' effect where a wedge of snow or gravel can build up in front of a locked wheel and help you stop - this may lengthen stopping distance but at least you should be able to steer. At all other times the ABS is a triumph of engineering safety that can counteract the tendency of the average driver to push the brake pedal to the floor and close their eyes - (and we all know that is all other people on the road, because we are all above-average or great drivers when we are behind the wheel).
I would leave the ABS connected, because 9 times out of 10 things are going to be better with it, and if you do disconnect it and you have an accident, you will maybe at best have no insurance cover, and at worst end up in jail.
if your car has traction control (or vehicle stability assist or whatever) it may be better in some situations to turn it off in loose snow- depends on the car, but at least there is a button for that and it will most likely come back on automatically when you start the car next time - because again 99 time out of 100 the car will be safer with it turned on.
here is a tip from and American car journalist -
Give yourself a brake. Learn how to get maximum efficiency from your brakes before an emergency. It's easy to properly use antilock brakes: Stomp, stay and steer. Stomp on the pedal as if you were trying to snap it off. Stay hard on the pedal. Steer around the obstacle. (A warning: A little bit of steering goes a very long way in an emergency. See Tip 8.) If you drive on icy roads or roads that are covered with snow, modify your ABS technique: After you "Stomp" and the ABS begins cycling — you will feel pulses in the pedal or hear the system working — ease up slightly on the pedal until the pulsing happens only once a second